SEATTLE — Machinists union members have ratified a new contract with Boeing Co., ending an eight-week strike that cut the airplane maker’s profits and stalled jetliner deliveries even as world demand was surging.

Workers are expected to return to Boeing’s commercial airplane factories, which have been closed since the Sept. 6 walkout, starting Sunday night.

The vote Saturday by members of the union, which represents about 27,000 workers at plants in Washington state, Oregon and Kansas, was about 74 percent in favor of the proposal five days after the two sides tentatively agreed to the deal and union leaders recommended its approval.

“This contract gives the workers at Boeing an opportunity to share in the extraordinary success this company has achieved over the past several years,” Mark Blondin, the union’s aerospace coordinator and chief negotiator, said in a union news release.

“It also recognizes the need to act with foresight to protect the next generation of aerospace jobs. These members helped make Boeing the company it is today, and they have every right to be a part of its future,” he said.

The union has said the contract protects more than 5,000 factory jobs, prevents the outsourcing of certain positions and preserves health care benefits. It also promises pay increases over four years rather than three, as outlined in earlier offers.

The union members, including electricians, painters, mechanics and other production workers, have lost an average of about $7,000 in base pay since the strike began. They had rejected earlier proposals by the company, headquartered in Chicago.

It was the union’s fourth strike against Boeing in two decades and its longest since 1995. The International Association of Machinists and Aerospace Workers staged strikes against Boeing for 24 days in 2005, 69 days in 1995 and 48 days in 1989.

“We’re looking forward to having our team back together to resume the work of building airplanes for our customers,” Scott Carson, Boeing Commercial Airplanes president and CEO, said in a statement. “This new contract addresses the union’s job security issues while enabling Boeing to retain the flexibility needed to run the business ... and allows us to remain competitive.”

The work stoppage was costing the company an estimated $100 million per day in deferred revenue and postponing delivery of its long-awaited 787 jetliner, which has already been delayed three times, and other commercial planes.

The strike came amid surging demand for Boeing’s commercial jetliners, which include 737s, 747s, 767s and 777s. Boeing has said its order backlog has swollen to a record $349 billion in value.

It remains unclear how long it would take Boeing’s commercial aircraft business to return to pre-strike production levels, but the company’s chief financial officer, James Bell, has said Boeing hopes it would take less than two months.

The walkout started as the global economy began sinking into turmoil. Boeing executives have said only 10 percent of the company’s orders come from domestic carriers, while the rest are placed by customers in other parts of the world, particularly Asia.

As the Machinists strike wore on, Boeing began talks with another union in hopes of avoiding a second strike by 21,000 scientists, engineers, manual writers, technicians and other hourly workers.

Boeing officials and representatives of the Society of Professional Engineering Employees in Aerospace, which struck for 40 days in 2000, moved into the final phase of contract talks Wednesday. The union’s two current contracts expire Dec. 1.

Negotiators at a hotel outside Seattle say they hope to present a proposal to that union’s membership by mid-November.

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